1. Field of the Invention
A subject matter of the invention is novel compounds capable of complexing carbon monoxide and their use in detectors for said gas.
2. Related Art
Semi-conducting metal oxides, such as ZnO, TiO2, SnO2, WO3 or Ga2O3, are very widely used as active supports for detectors for carbon monoxide. The essential characteristic of these compounds is their high sensitivity for carbon monoxide; however, their operating temperature is high (=350° C.).
Other metal oxides, those having a perovskite structure (ABO3, where A and B are different metals), have been tested for detecting carbon monoxide. These compounds have good sensitivity for this gas with lower operating temperatures, of the order of 150-200° C.
Hemoglobin, myoglobin and their models are capable of coordinating oxygen and carbon monoxide in solution at ambient temperature. This coordination occurs at the iron (II) atom of the hemoprotein. For this type of compound, the selectivity for one or other of the gases is given by M, which is the ratio of the partial pressures at half-saturation of the two gases1.M=P1/2O2/P1/2COA high value of M reflects a greater affinity for carbon monoxide than for oxygen.
Myoglobin, for which M is between 20 and 40, and hemoglobin, for which M is approximately equal to 150, have a high affinity for oxygen at ambient temperature.
On the other hand, the compound known as (To-PivPP) Fe (1,2Me2Im) and represented by FIG. 1, for which the value M in solution at ambient temperature is of the order of 4 000 with a carbon monoxide half-saturation partial pressure (P1/2CO) approximately equal to 9×10−3 Torr (1 Torr=1 mm Hg=105 Pa/760), has more affinity for carbon monoxide than for oxygen at ambient temperature. However, the long-term stability of compounds of this type is limited, in particular because of the oxidation of iron(II) to iron(III) in air in the presence of moisture, which then inhibits any subsequent coordination of carbon monoxide.